Known systems simultaneously display a horizon line, a slope scale and a speed vector symbol that allow the pilot to view the slope of the aircraft easily via the relative position of the speed vector symbol with respect to the horizon line.
During the landing of aircraft, the pilot uses the displayed horizon line to position the slope of the aircraft relative to the runway. He gradually raises the speed vector symbol relative to the horizon line, during the flare phase, above the runway, so as to place the speed vector symbol below the horizon line, at a predetermined distance therefrom corresponding to a target slope, for example approximately 1° below the horizon line, before touching down with the wheels. Such a maneuver allows a comfortable touchdown of the aircraft on the runway.